The object of the invention is to simplify as far as possible the manoeuvres to be carried out by an operator and to facililate docking of the structure, as well as to reduce as far as possible the energy required to lock and unlock said system on the structure, while procuring a significant clamping free from backlash insensitive to temperature variations and not requiring any lubrication. The system according to the invention makes it possible to obtain and ensure a minimum gripping force, with low-amplitude handling on a structure whose dimensions may be subject to large dispersion. Moreover, the system according to the invention makes it possible to prevent the operator from experiencing any sensation of handling forces, since it comrpises free limit stops materializing the various locking stages on the structure.